The present invention relates to a circuit for receiving High Definition Television (hereinafter referred to as HDTV) signal and signal processing method therefor by using a frequency band splitting and sub-sampling methods in HD TV picture receiver.
HDTV has been researched by Japan since 1960 as a way to improve picture quality of conventional color TV. Emphasis of the research has been laid on getting more dynamic and lively picture quality, aiming at providing a high quality picture equivalent to the picture quality enjoyed in ordinary movie theaters. Japan's lead in the HDTV research had been continued until early 1980's, however, other countries have also started to move into the research since mid 1980's.
Japan has completed development of multiple subnyquist sub-sampling encoder (hereinafter referred to as MUSE) method for HDTV centered around NHK while Europe has been developing HD-MAC method that is completely different from the MUSE method of Japan. In U.S.A., number of methods are suggested but none of the methods have become a standard yet. The methods suggested in U.S.A. are AC-TV of DSRC, spectrum-compatibility HD-TV of Zenith, Mit of MIT, and SLSC of Bell Laboratory. The MUSE employs multiple sub-sampling technique. The Mit method employs Sub-band coding technique. Basically, types other than the above methods mostly adopt techniques described above.
However, in the current research and development of the HDTV broadcasting technique, it is demanded that not only high quality picture but also compatibility with existing color TV (NTSC color television) should be achieved.
The MUSE method of NHK of Japan is not compatible with existing color TV, but the AC-TV method of the DSRC which is one of the several HDTV methods suggested in U.S.A., multiplexes other TV signals with existing color TV signals (NTSC signal) so as to be compatible with the existing color TV. However, the AC-TV method of the DSRC has number of technological problems to be resolved, and particularly, is known to have limits in getting higher frequency band in processing TV signals.
It is newly demanded, as a way to solve the problems raised in the AC-TV, that the HDTV signals adopt the same frequency band as that of the existing color TV, while keeping the compatibility with the existing color TV. In this case, the channel unused in the existing color TV is used to transmit the HDTV signal.